Fifteen years ago, Ben Walker (Kevin Sorbo) decided to leave his college sweetheart Wendy (Kristy Swanson), and ultimately his faith, in order to pursue a lucrative business opportunity (graduating top of his class from Harvard Business School instead of receiving a doctorate in Theology with a minor in Biblical Archaeology).
In the present, Ben has become a financial wizard as the head of his company, and has just proposed marriage to a pretty yet materialistic fiancée. When his car breaks down on the way to the airport, he is visited by a gruff yet angelic mechanic (John Ratzenberger), who tells him that he needs to see what his life would have been like had he followed God's calling. Suddenly, Ben finds himself in an alternate reality married to Wendy with two daughters - rebellious teen Kimberly (Debby Ryan), and Kimberly's little sister, Megan (portrayed by newcomer Taylor Groothuis) - getting ready for church on a Sunday morning, where he's scheduled to give his first sermon as the new pastor. The mechanic explains that this is an experience God has put in place to show Ben what would have happened if he'd accepted his other calling, the great "What If".
If Ben wants to get back to his old life, he must first learn to appreciate the value of faith and family, and perhaps rediscover the love of his life. In the tradition of It's a Wonderful Life and The Family Man, What If... tells the story of a man whose glimpse into what he's missing reminds him of what he truly wants.